Re: carbon


Sam Hoskins
 

All,

I truly hope that we don't get off on the wrong foot with someone new to the
Q world, especially someone who has already built seven aircraft. It sounds
like Bob Cringely can bring a lot to the table. There are newer ways to
skin the old cats around here, and we need to keep our eyes/ears open when
the potentially good ideas surface.

Having said that, Bob probably does not have the benefit of having read
thousands of posts on the Q-list, the contributions to the newsletter, or
the experiences many of us have been through. Having been in aviation as
long as he has, I'm sure that he also has "seen em' come and seen em' go".
(Google Bob and you might be surprised what you come up with). Several times
a year a Quickie newbie may pop up and propose all sorts of unusual ideas,
that never make it to fruition; the latest, a turbine powered Quickie, comes
to mind. The Q-group is weary of these Johnny come lately's and justifiably
wary of them.

Bob also may not know that we have an entirely separate e-mail list, just
for discussions of non-standard Q related mods. You can join here:
http://groups.yahoo.com/group/Q-Performance/ This was created to try and
avoid confusion when attempting to build a standard Quickie type plane.
Admittedly, the line sometimes blurs.

We all need to keep in mind that there is a world outside or ours and a lot
of people can bring things to the table. The trick is separating the wheat
from the chaff. I think Bob may be good for us.

Personally, I sincerely hope Bob sticks around and I hope he builds his CF
Quickie. However, that discussion is most appropriate on the Performance
list.

Good luck and stay friendly.

Sam Hoskins
Murphysboro, IL
www.samhoskins.blogspot.com



On Sun, Dec 20, 2009 at 3:17 PM, Mike Perry <dmperry1012@...> wrote:



Bob:

Someone is crazy here. I don't think it's Lynn French. Your recent
posts contains some interesting insights mixed with some half truths and
some gross errors. Let's start with your comments about Burt Rutan.

1) The Q2 is NOT a Rutan design and he objects vigorously to being
associated with it. You seem to mix comments on the Q1 with the Q2
without realizing that.
2) The wing spar takes the main load but what prevents torsion
(twisting)? Some part of the structure has to prevent twisting, what is
it? I do not know the context of Burt's remarks about the skins not
carrying the loads but I do not think the foam alone is enough to resist
twisting in any Q wing. BTW, just what is the "spar" in the Q wing?
3) "[Burt's] spars were designed with ultimate loads double the service
loads as opposed to 1.5X in a metal structure." That is an FAA standard
for composite structures and a generally accepted criteria in
engineering work with composites. This is based on the failure mode of
composites and on variability in materials and construction. There are
whole books written on this, I'm not reproducing them here.
4) "[Burt's] design process was always minimal while his testing was
rigorous." Great. Just who tested the Q-2 wing? Or the Q-1 wing for
that matter? If QAC tested them there is no record I know of.

This seems to be the right point to inject that I tested a Q2 wing. The
results will be in the next Q-talk. There were several problems with
the test, so I don't think we can say much about the safety of the Q2
wing; however, the wing broke at 7.5 Gs (design limit 12 Gs) with a
failure that appeared torsional. It started just outside of an area
that was repaired and reinforced for testing purposes -- it certainly
seemed like a minor change that would make the overall wing stronger,
but instead the wing broke early. That experience makes me very
skeptical of people who say these wings are over-designed, or who say
the skins aren't important for torsion resistance, or who substitute
materials without engineering and testing.

Returning to your posts, you wrote, "The only real structural change was
adding carbon spars to the canard and that was in an attempt to keep bad
pilots from breaking their planes during Pilot-Induced-Oscillation (PIO)
on landing." Really? I'm glad to hear it wasn't needed to increase the
gross weight of the airplane or to change to a thinner airfoil that was
less susceptible to surface contamination, esp. rain.

You also wrote, "So on wings of this type (where the spars carry the
majority of loads) a single layer of cloth on the 45-degree bias offers
enough strength to carry any torsion loads and keep the insides of the
wing on the inside." Which cloth? Surely not UNI. Has a single layer
of BID been tested in this application? Based on the wing test I did I
would strongly disagree with this advice.

You also wrote, "What is the history of structural failures on Quickies?
Zero." If you mean only the single seat Quickie I am not aware of any
structural failures, but there have been main wing failures in the Q2.
Two Q-2 wings failed due to non-standard construction (building a core
from smaller blocks) or a non standard repair (using expanding foam).
This makes me suspicious when people propose "minor" changes or
substitutions because the airplane is "so over-built that you can make
lots of changes with relative impunity."

You also wrote, "I'm not cutting any foam for my Q. I'm making female
molds for all the parts and will vacuum bag and cure them at 250 degrees
in my home-made oven. I expect to finish the plane by September."
Great. Please stop calling this airplane a Q, Q1 or Quickie. You are
talking about a totally redesigned airplane.

THIS DISCUSSION BELONGS ON Q-PERFORMANCE. You are talking about an
entirely new design. This is not about building testing and flying a
standard Quickie or Q2xx.

I am not an engineer. From what I read neither are you. For your
safety I recommend you get one involved, or do a lot of testing, or both.

Mike Perry


bob@... <bob%40cringely.com> wrote:


I don't know how to put this politely, but are you CRAZY?

I fly 300+ hours per year entirely in experimental aircraft. Next year
I will go to California (I live in South Carolina) 18 times -- all at
16-18K. So I have quite a bit of experience doing just the sort of
flying you describe. In my youth (I am 56) I went as high as 22K
without oxygen -- ONCE. Today I use O2 fulltime at night (no matter
what altitude) and above 8000 during the day. What you propose to do
is insane.

Bob




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